https://www.socialeurope.eu/2017/07/what-can-we-learn-from-the-nordic-model/
https://blogs.lse.ac.uk/europpblog/2021/10/22/de-facto-differentiation-in-action-why-poland-will-stay-in-the-eu-with-or-without-the-blessing-of-brussels/
https://ec.europa.eu/commission/presscorner/detail/en/ip_20_181
https://www.bloomberg.com/news/articles/2017-06-14/ryanair-easyjet-say-soft-brexit-won-t-address-airline-concerns?cmpid=BBBXT061517_BIZ&utm_medium=email&utm_source=newsletter&utm_term=170615&utm_campaign=brexit